1. Field of the Invention
The present invention relates to an arrester, which may be used, for example, as an over-voltage suppression unit in an electric power transmission system. The present invention also relates to an arrester assembly incorporating a plurality of arresters, and to a method of forming an arrester assembly.
2. Summary of the Related Art
It is normal to transmit electric power from the site at which it is generated, e.g. a power station, to the sites where it is to be used, by overhead cables. If such cables are struck by lightning, an over-voltage appears on the cables which may result in damage to electrical devices connected to the transmission system. For this reason, it is common to connect one or more arresters to electrical power transmission systems, which arresters act as overvoltage suppression devices.
There are many different types of arresters. In one known type, the arrester is in the form of a column, having a plurality of conductive elements which are laminated together. The conductive elements have a non-linear characteristic. This may be achieved by making them of a suitable material, such as zinc oxide. In known examples of such arresters, the conductive elements have an annular cross-section and are mounted on an insulating rod.
The over-voltage suppression effect of such an arrester depends on the number and thickness of the conductive elements. In order to prevent the arrester from becoming too long, it has been proposed that a plurality of laminated columns be provided, arranged in parallel, with the columns being electrically connected together. In this way, by forming a conduction path extending along and between the columns (by use of suitable electrical connection members interconnecting the columns at intermediate points along their length), it is possible to provide a sufficiently long conduction path without making the arrester excessively long. Examples of such arresters are disclosed in JP-A-56-91402 and JP-A-56-164502.